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node.jsanimationthree.js3dparticles

THREE.js BufferGeometry points animate individually around sphere and control speed


So im going nuts lol this seems to be super easy and I feel like im so close but I cant seem to pin point where im going wrong here.
. Im trying to create an animated group of THREE.js BufferGeometry Points, and animate them around a sphere pattern INDIVIDUALLY at different speeds and have them start at different positions. I want them to each animate in a circular motion around the sphere pattern, not shoot randomly around like i have them now. They can BEGIN in any random spot but where they start, they should begin on a straight, normal circular pattern around the sphere. Also, my issue is figuring out how to SLOW THEM DOWN.

From what I understand, theta, is the angle which needs to b increased to rotate a particle around a sphere. So im kinda lost how to do that properly. below is my code and codepens, any advice is greatly appreciated and try to dumb it down for me on the math terminology as im super new to vector math but have been studying to try and learn some cool sh!t

Primarily, there are two main parts. The initial loop which does the initial drawing/placement of the particles and the second loop which udpdates them and is meant to move them forward in their circular future path around the sphere pattern. If thats not the correct way to go about this, please lmk lol.

Initial placement of particles in random places all along the outside of a spherical pattern and my update function is the same as of now although im sure the update function is the one that needs to change:

    const t = clock.getElapsedTime();
    let theta = 0, phi = 0;
    for (let i = 0; i < 1000; i++) {
      theta += 2 * Math.PI * Math.random();
      phi += Math.acos(2 * Math.random() - 1);
      const x = radius * Math.cos(theta) * Math.sin(phi)
      const y = radius * Math.sin(theta) * Math.sin(phi)
      const z = radius * Math.cos(phi)

      positions.push(x, y, z);
        sizes.push(Math.random()*100)
        const hex = colorList[Math.round(Math.random() * colorList.length)]
        const rgb = new THREE.Color(hex)
        colors.push(rgb.r, rgb.g, rgb.b)
    }

jsfiddle

The Vue tab in the fiddle has all the code.

Ive tried the above with a time constant added to theta and without and all the particles move about randomly around the sphere, but I cant figure out how to get the particles to moe in a smooth, slower, circular pattern around the sphere. Again, the initial random positions are fine, but the way they update and scatter around randomly is wrong, i know it has to do with the theta variable i just cant figure out what to do to make it right.


Solution

  • Ok, after what seems likes months, I FINALLY figured out how to INDIVIDUALLY rotate three.js points around a sphere at different speeds, from random starting positions.

    THERE ARE LOTS OF EXAMPLES FOR OLD THREE.JS VERSIONS THAT USE THREE.GEOMETRY, BUT THIS USES THE NEW BUFFERGEOMETRY WITH THE LATEST THREE.JS VERSION, NOT SOME ANCIENT R86 VERSIO LIKE THE OTHER EXAMPLES!!!

    This first part does the initial plotting of the points

    
      const radius = 1.5
      const vectors = []
      let theta = 0; let phi = 0
      for (let i = 0; i < 5000; i++) {
        theta = 2 * Math.PI * Math.random()
        phi = Math.acos(2 * Math.random() - 1)
    
        const px = radius * Math.cos(theta) * Math.sin(phi)
        const py = radius * Math.sin(theta) * Math.sin(phi)
        const pz = radius * Math.cos(phi)
    
        const vertex = new THREE.Vector3(px, py, pz)
        vertex.delay = Date.now() + (particlesDelay * i)
        vertex.rotationAxis = new THREE.Vector3(0, Math.random() * 2 - 1, Math.random() * 2 - 1)
        vertex.rotationAxis.normalize()
        vertex.rotationSpeed = Math.random() * 0.1
        vectors.push(vertex)
    
        positions.push(vertex.x, vertex.y, vertex.z)
        sizes.push(Math.random() * 0.1)
        const hex = colorList[Math.round(Math.random() * colorList.length)]
        const rgb = new THREE.Color(hex)
        colors.push(rgb.r, rgb.g, rgb.b)
      }
    
      geometry.setAttribute('position', new THREE.Float32BufferAttribute(positions, 3).setUsage(THREE.DynamicDrawUsage))
      geometry.setAttribute('color', new THREE.Float32BufferAttribute(colors, 3))
      geometry.setAttribute('size', new THREE.Float32BufferAttribute(sizes, 1))
    
      const particles = new THREE.Points(geometry, shaderMaterial)
      scene.add(particles)
    
    

    This is the magic that updates the points around the sphere

     const posAttribute = particles.geometry.getAttribute('position')
      const ps = posAttribute.array
    
      const updateParticles = () => {
        // loop over vectors and animate around sphere
        for (let i = 0; i < vectors.length; i++) {
          const vector = vectors[i]
          vector.applyAxisAngle(vector.rotationAxis, vector.rotationSpeed)
    
          ps[i * 3] = vector.x
          ps[i * 3 + 1] = vector.y
          ps[i * 3 + 2] = vector.z
        }
    
        particles.geometry.attributes.position.needsUpdate = true
      }